Synthesis and regulation of the single-stranded RNA viral genomes of picornaviruses and influenaz viruses will be studied. These viruses are human pathogens and influenza is still a leading cause of morbidity and mortality in man. To determine the components involved in the synthesis of viral RNA, virus-specific structures will be isolated from infected cells. The chemical composition and functional significance of the membranes, proteins, and virus-specific RNA's associated with these structures will be analyzed. Comparisons will be made with virus-specific structures isolated during restricted replication of viral genomes using temperature-sensitive mutants, selective viral inhibitors, and host- dependent restriction. Specific interactions between viral RNA and proteins in the formation of ribonucleoprotein structures (RNP's), and the significance of RNP's in replication an translation of viral RNA will be investigated. A major effort will be made to develop in vitro systems for the study of the detailed mechanism and control of viral RNA synthesis. Influenza virus replication requires a host cell function which can be measured by sensitivity to dichlorobenzimidazole riboside, actinomycin D or alpha-amanitin. Since growth of influenza virus is more resistant to actinomycin D in transformed cells, the replication of RNA will be studied in both normal and tranformd cells. The knowledge obtained from these studies should lead to a rational approach for the selection of specific chemical inhibitors that can interrupt critical steps in the replication of RNA genomes, and it should make possible a better understanding of host-dependent differences in the regulation of synthesis of viral RNA.